This invention relates to a novel sunflower hybrid, to products obtained from the novel hybrid, and to methods for producing the sunflower products.
The sunflower (genus Helianthus) is second only to the soybean as a source worldwide for vegetable oil. In the United States there are approximately four million acres planted annually in sunflower, primarily in the Dakotas and in Minnesota. Average sunflower yields in the United States range from about 1200 to about 1400 kg/hectacre, with the oil content from harvested seed averaging about 44% on a dry weight basis. Increasing both yield and oil content are currently major objectives in sunflower breeding programs in the United States, Canada, the USSR, and elsewhere; other objectives of such programs include earlier plant maturity, shorter plant height, uniformity of plant type, and disease and insect resistance.
The very rapid expansion over the last decade of acreage planted in sunflower in the United States is due in part to several important developments in the field of sunflower breeding and varietal improvement. One significant development was the discovery of cytoplasmic male sterility and genes for fertility restoration, a discovery that allowed for the production of hybrid sunflower. The hybrids thus produced were introduced during the early 1970's. They showed about a 25% yield advantage over the open-pollinated varieties, improved disease resistance, greater uniformity in height and flowering; and a greater degree of self-compatibility, which alleviates the dependency on high insect pollinator populations for good seed set.
A description of cytoplasmic male sterility (CMS) and genetic fertility restoration in sunflowers is presented by Fick, "Breeding and Genetics," in SUNFLOWER SCIENCE AND TECHNOLOGY 279-338 (J. F. Carter ed. 1978), the contents of which are incorporated herein by reference. The production of a particular sunflower hybrid using CMS is described in U.S. Pat. No. 4,378,655, the contents of which are also incorporated herein by reference. Although cytoplasmic male sterility is now the technique of choice for producing sunflower plants with substantially non-functional pollen for subsequent use in producing hybrids, other methods, also described in the aforementioned U.S. patent, are available. These include the use of complete or partial genetic sterility based on the presence of recessive genes and the application of chemical gametocides. Plants having a high level of self-incompatibility can also be used in a method for hybrid production.
Another important development in sunflower breeding was the introduction into the United States of high oil varieties from the USSR in the mid-1960s. These varieties had oil percentages (total oil relative to seed weight) in the range of 40-45% as compared to 30-35% for varieties grown previously. The oleic acid percentage for the oil of these and other commercially grown varieties varied, especially with environment, but rarely exceeded 40 percent. In the late 1970's researchers in the USSR reported in the the production by chemical mutagenesis of an open-pollinated sunflower cultivar ("Pervenets") which produced an oil having an oleic acid content, expressed as percentage of total fatty acid content, of approximately 70% to 80%, with proportionately less linoleic acid. See Soldatov, "Chemical Mutagenesis in Sunflower Breeding," in PROC. 7th INT'L SUNFLOWER CONF. (Krasnodar, USSR 1976) 352-57. Pervenets germplasm became generally available to sunflower breeders in the United States after 1980.
Sunflower oil is comprised primarily of palmitic, stearic, oleic, and linoleic acids, with oleic and linoleic accounting for about 90% of the total fatty acid content in conventional oils. It has been recognized that there was an inverse relationship between oleic and linoleic acid which was highly influenced by environment, especially temperature during the growing season. Heretofore, cool northern climates yielded high linoleic acid-content sunflower seed, whereas high oleic acid values were characteristic of seed grown in warmer southern areas. While a high linoleic acid concentration is desirable in sunflower oils used in soft margarines and salad dressings, a high oleic acid content is preferred for many other applications, since oleic acid is oxidatively more stable than linoleic acid. As a consequence, oxidative stability of conventional crude sunflower oil derived from seed grown in southern climates is nearly twice that of crude oil extracted from northern-grown seed.
With the Pervenets cultivar, however, an increase in oleic acid percentage of total fatty acid content from 64% to 79% during seed formation and ripening was observed in conjunction with a decrease in linoleic acid of from 26% to 15%, see Soldatov, supra, compared to a 21-54% increase in the linoleic acid content of conventional seed. Moreover, while higher growing temperatures promoted rapid oleic acid development in Pervenets plants, the comparatively higher oleic acid-linoleic acid content ratio characteristic of the cultivar remained substantially unaffected by environmental conditions. See Kharchenko, "Genotypic and Phenotypic Mechanisms Ensuring Regulation of Fatty Acid Biosynthesis in Sunflower Seeds," Fiziologiya Rastenii (Russian) 26:1226-32 (1979).
The development of the Pervenets cultivar therefore held particular significance for the possible enhancement of oxidative stability in sunflower oils. As an open-pollinated cultivar, however, Pervenets is heterogeneous for high oleic acid content; that is, individual plants producing various levels of oleic acid are present in the variety and the high oleic trait is not expressed reproducibly over many generations of sunflower plantings. Even for those Pervenets sunflower plants which do produce high oleic seed, the content of linoleic acid, expressed as percentage of the total amount of fatty acids, can be substantial, ranging as high as 26% or more. See Soldatov, supra at page 356. Moreover, the Pervenets cultivar does not consistently express various other characteristics, such as adequate disease resistance, which may be critical to the commercial viability of a new crop. Pervenets seed is also basically indistinguishable from the black or black-and-gray striped seed produced by conventional, commercially grown oilseed sunflower hybrids. As a consequence, Pervenets seed cannot be readily recognized as such, if it is mixed with other oilseed at some point during the multi-stage processing of seed into oil.